Phase shifters are used in many electronic applications for altering the phase of the output signal in a transmission line. Phase shifters are a key functional component in a large number of modern communication systems, including direct satellite systems (DSS) receivers, digital cellular phones, satellite modems, and wireless local area network (LAN) modems. For example, phase shifters are used to trim the delay time of microwave signals in passive or active networks; to change the amplitude and phase of a received signal in an RF system; to control the linear phase of an amplifier provided at an transmitter/receiver of a mobile communication system; to adjust the beam scan angle of a base station antenna; and to control the phase of an output signal of a band pass filter or a duplexer. One important application of phase shifters is in digital phase-locked loops (PLL) to remove phase and/or frequency errors from received signals. Another is in phased array antennas. A phased array antenna is an antenna configuration composed of a large number of elements that emit phased signals to form a radio beam. The radio signal can be electronically steered by active manipulation of the relative phasing of the individual antenna elements. By incorporating a network of phase shifters, a phased array antenna can be pointed electronically in microseconds, without any physical realignment or movement of the antenna or its elements. Beam steering improves the carrier-to-interference ratio of the received signal by attenuating unwanted sources of interference.
Tunable phase shifters may be controlled electrically, magnetically or mechanically. Many electrical phase shifters use varactor diodes (the capacitance of which changes with voltage) or ferroelectric materials (the permittivity of which changes with electric field strength) as the phase modulating element. Tuning of the varactor capacitance or ferroelectric permittivity causes a change in phase when an RF signal passes through the phase shifter.
An issue with varactor diodes is that they consist of many components. They are expensive to make and require regular adjustment. Ferroelectric phase shifters, on the other hand, present their own problems. The integration of ferroelectric materials within an integrated circuit is challenging, high voltages are required to operate ferroelectric phase shifters, and the design of the phase shifter is complicated because the properties of ferroelectric materials are different from the properties of conventional dielectric materials used in transmission lines.
The apparatus and associated methods disclosed herein may or may not address one or more of these issues.
The listing or discussion of a prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the present disclosure may or may not address one or more of the background issues.